Photoactivated Activities on Spodoptera litura Cell, Singlet Oxygen and Photostability of Photosensitizers

[Objective ]The aim of this study was to improve the photostability of pho-tosensitizers. [Method] 2,5-Diphenylthiophene and 2,5-dithienylethynylthiophene were synthesized by replacing thiophene rings of α-terthienyl （α-T） with benzene rings. Photoactivated activities on Spodoptera litura （SL） cells, singlet oxygen with UV and photostability of photosensitizers were investigated. [Result] The cytotoxicity of pho-tosensitizer 2,5-diphenylthiophene on SL cells was 0.22 and 0.16 μg/ml after treat-ment for 24 and 48 h, respectively, while that of 2,5-dithienylethynylthiophene on SL cells was 0.06 and 0.04 μg/ml. Singlet oxygen of 2,5-diphenylthiophene and 2,5-dithienylethynylthiophene was 1.047 5, 1.529 4 μg/mmol under UV, respectively. Degradation dynamic equations of 2,5-diphenylthiophene and 2,5-dithienylethynylthio-phene in methanol were Ct= 5.227 1e-0.006 1t, Ct= 5.084 2e-0.097 3t and half life was 111.79, 7.12 h. [Conclusion] Photosensitizer 2,5-diphenylthiophene has high singlet oxygen production ability, and high photoactivated cytotoxicity on SL cells under UV. Moreover, 2,5-diphenylthiophene has overcome the deficiency of photoactivated in-secticides, which is not applied directly in field because it degrades quickly in the environment.

Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton

In recent years,there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen(1O_(2));however,there are few studies on the synergistic effect of 1O_(2) and free radicals on the degradation of organic molecules,such as phenol in Fenton reaction.In this study,a cocatalyst,CoP,commonly used in photocatalysis was synthesized using a simple two-step method,and a CoP/Fe^(2+)/AM1.5 system was constructed by introducing Fe^(2+)and simulated sunlight(AM1.5)irradiation.The newly constructed CoP/Fe^(2+)/AM1.5 system could effectively degrade various organic pollutants,including dyes,phenols,and antibiotics.Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species(ROS)in the CoP/Fe^(2+)/AM1.5 system,including·OH_(ads),·O_(2)^(-),and 1O_(2).Further,combined with the liquid chromatogram of phenol,its intermediate products,and the fluorescence diagram of o-hydroxybenzoic acid,it can be concluded that a synergistic effect exists between 1O_(2) and the surface-adsorbed·OH_(ads) in the CoP/Fe^(2+)/AM1.5 system.The controllable formation of surface 1O_(2) and·OH_(ads) was achieved through the oxidation(Co^(3+))and reduction(Pδ−)centers exposed on the CoP surface,and the synergistic effect between them results in phenol’s hydroxylation,ring-opening,and degradation.The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

Emerging Strategies in Enhancing Singlet Oxygen Generation of Nano-Photosensitizers Toward Advanced Phototherapy

The great promise of photodynamic therapy(PDT) has thrusted the rapid progress of developing highly effective photosensitizers(PS) in killing cancerous cells and bacteria. To mitigate the intrinsic limitations of the classical molecular photosensitizers, researchers have been looking into designing new generation of nanomaterial-based photosensitizers(nano-photosensitizers) with better photostability and higher singlet oxygen generation(SOG) efficiency, and ways of enhancing the performance of existing photosensitizers. In this paper, we review the recent development of nano-photosensitizers and nanoplasmonic strategies to enhance the SOG efficiency for better PDT performance. Firstly, we explain the mechanism of reactive oxygen species generation by classical photosensitizers, followed by a brief discussion on the commercially available photosensitizers and their limitations in PDT. We then introduce three types of new generation nanophotosensitizers that can effectively produce singlet oxygen molecules under visible light illumination, i.e., aggregation-induced emission nanodots, metal nanoclusters (< 2 nm), and carbon dots. Different design approaches to synthesize these nano-photosensitizers were also discussed. To further enhance the SOG rate of nano-photosensitizers, plasmonic strategies on using different types of metal nanoparticles in both colloidal and planar metal-PS systems are reviewed. The key parameters that determine the metal-enhanced SOG(ME-SOG) efficiency and their underlined enhancement mechanism are discussed. Lastly, we highlight the future prospects of these nanoengineering strategies, and discuss how the future development in nanobiotechnology and theoretical simulation could accelerate the design of new photosensitizers and ME-SOG systems for highly effective image-guided photodynamic therapy.

SINGLET OXYGEN QUANTUM YIELDS OF PORPHYRIN-BASED PHOTOSENSITIZERS FOR PHOTODYNAMIC THERAPY

The major cytotoxic agent with most current photosensitizers used in photodynamic therapy(PDT)is widely believed to be singlet oxygen(^(1)O_(2)).Determination of the ^(1)O_(2) quantum yields for porphyrin-based photosensitizers,including hematoporphyrin derivative(HiPorfin),hematoporphyrin monomethyl ether(HMME)and photocarcinorin(PsD-007)in air-saturated dimethylformamide(DMF)solutions were performed by the direct measurement of their near-infrared luminescence.In addition,^(1)O_(2) quencher sodium azide was employed to confirm the ^(1)O_(2) generation from the investigated photosensitizers.The maximal ^(1)O_(2) luminescence occurs at about 1280 nm with full width at half maximum of 30 nm.The ^(1)O_(2) quantum yields were found to be 0.61±0.03,0.60±0.02 and 0.59±0.03 for HiPorfin,HMME and PsD-007,respectively.These results provide that these porphyrin-based photosensitizers produce ^(1)O_(2) under irradiation,which is of significance for the study of their photodynamic action in PDT.

A High Sensitivity Detection Method of Singlet Oxygen and Superoxide Anion

This paper, for the first time, reports a method that can be used as a highly sensitive probe for singlet oxygen (1O2) and superoxide anion (O2-) in vitro or in vivo. FCLA(3,7-dihydro-6-{4-[2-(N'-(5-fluoresceinyl)thioureido)ethoxy]phenyl}-2-methylimidazo{1,2-a}pyrazin-3-one sodium salt), a chemiluminescence (CL) analysis reagent, has been reported to sensitively react with 1O2 and O2- to emit photons with a spectral peak of 525nm. In this work, when human serum albumin (HSA) was added into FCLA solution to enhance the CL intensity, approximately 20 times, compared to that without HSA. The enhanced CL had the same 525 nm spectral peak, identical to that without HSA. By gradually reducing the molecular oxygen content in the solution, we find that the auto-oxidation of oxygen molecules dissolved in the solution plays an important role in the CL process. Based on these experimental evidences, we propose a novel and highly sensitive detection method of 1O2 and O2-, which may have a great potential in chemical and medical applications.

SINGLET OXYGEN DETECTION DURING PHOTOSENSITIZATION

Singlet oxygen(^(1)O_(2))is a highly reactive oxygen species involved in numerous chemical and photochemical reactions in diferent biological systems and in particular,in photodynamic therapy(PDT).However,the quantifcation of^(1)O_(2) generation during in vitro and in vivo pho-tosensitization is still technically challenging.To address this problem,indirect and direct methods for^(1)O_(2)detection have been intensively studied.This review presents the available methods currently in use or under development for detecting and quantifying^(1)O_(2) generation during photosensitization.The advantages and limitations of each method will be presented.Moreover,the future trends in developing PDT-^(1)O_(2) dosimetry will be briefly discussed.

Correlation of in vivo tumor response and singlet oxygen luminescence detection in mTHPC-mediated photodynamic therapy

Excited-state singlet axygen(^(1)O_(2)),generated during photodynamic therapy(PDT),is believed to be the primary cytotoxic agent with a number of clinically approved photosensitizers.Its relative concentration in cells or tissues can be measured directly through its near-infrared(NIR)luminescence emission,which has correlated well with in vitro cell and in triro normal skin treatment responses.Here,its correlation with the response of tumor tiss1e in vito is examined,using the photosensitizer meso-tetralydroxyphenylchlorin(mTHPC)in an animal model comprising luciferase-and green fluorescent protein(GFP)-transduced gliosarcoma grown in a dorsal window chamber.The change in the bioluminescence signal,imaged pre-treatment and at 2,5 and 9 d post treatment,was used as a quantitative measure of the tumor response,which was classified in individual tumors as"non","moderate"and"strong"in order to reduce the variance in the data.Plotting the bioluminescence-based response vs the^(1)O_(2)counts demonstrated clear correlation,indicating tha^(1)O_(2)luminescence provides a valid do-simetric technique for PDT in tumor tissue.

Synthesis and photochemistry of novel bromo substituted stilbene derivatives as triplet state sensitizers for the generation of singlet oxygen

We have presented the synthesis and characterization of three new bromo substituted stilbene derivatives, p-3,4,5-trimethoxy-p′- 2,3,4,5,6-pentabromostilbene （C1）, p-N,N-dimethylamino-p′-2,3,4,5,6-pentabromostilbene （C2） and p-N,N-diphenylamino-p′- 2,3,4,5,6-pentabromostilbene （C3） in this letter. The UV/vis absorption and photoluminescence were investigated in various solvents. The maximal absorption wavelength of C1 exhibited blue-shift to those of C2 and C3 in different solvents. No florescence emission could be detected for these compounds at room temperature. Singlet oxygen could be efficiently produced with these sensitizers under near-ultraviolet and visible light irradiation.

Capacity of Tea Scavenging Singlet Oxygen Studied by Means of 1,3-Diphenylisobenzofuran as Fluorescence Probe

In recent years, the effects of reactive oxygen species（ROS） generated in the course of biological metabolism, such as superoxide（O2 ）, hydrogen peroxide（H202）, hydroxyl radical（HO） and singlet oxygen（102） on the human health have received more attention due to their vital roles in physiological functions. Normally, antioxidant molecules, superoxide dismutase and catalase in biological organism can scavenge excessive free radicals by a series of chemical reactions to keep the cells in a state of redox homeostasis. Once the homeostasis has been broken,

An ESR Study on Singlet Oxygen Photoproduction of the Meso-Tetrakis-(Substituted Phenyl) Porphine Derivatives

The ability of meso-tetrakis- (substituted phenyl) porphine derivatives for photo-generating singlet oxygen (O2) is studied by ESR spectrometry. The results show that the singlet oxygen yields of most of porphine derivatives are higher than that of HPD. It is also exhibited that the nature and structure of the substituent at the meso position are closely related to the photo-sensitizing ability of meso-tetrakis-(substituted phenyl) porphine.

A Singlet State Generated with SQUIDs in Cavity QED

We propose a scheme to generate a three-qubit three-IeveI singlet state in cavity QED, by placing three A-type SQUIDs in a single mode cavity. In this scheme, we make use of the interaction between the SQUIDs and cavity filed, and the classical pulses. The cavity fields are in vacuum state during the whole operation processes of creating the entanglement, and there is no quantum information transformation between the SQUIDs and cavity fields. Because of the advantage of the SQUID-cavity system, the quality factor of the cavity is greatly relaxed.

Study on the Total Synthesis of Hainanolide (V)-Oxidation of the Tricyclic Alkenes with Singlet Oxygen

Six tricyclic compounds containing C-3, C-4 double bonds were oxidized with singlet oxygen. Different regio-selectivity was found with regard to steric hinderence.

Synthesis,Characterization,and Linear and Nonlinear Optical Properties of Phenylene-vinylene Based Chromophores for Singlet Oxygen Generation

A series of symmetrical and unsymmetrical phenylene-vinylene （PV） based chro- mophores with the molecular configuration of donor-π-donor （D-g-D） were prepared and characterized. Iodine was first introduced into the Jr-conjugation backbone of the PV based chromophores in order to study the heavy atom effect on their linear absorption, two-photon absorption （TPA） properties, as well as singlet oxygen generation properties. TPA cross-sections of these chromophores were investigated by using the two-photon excited fluorescence method. The unsymmetrical chromophores were found to have larger TPA cross-section values compared to their symmetrical counterparts. For one of the unsymmetrical chromophores with the iodine incorporation, a large TPA cross section value with quenched emission was found. The decreased fluorescence quantum yield of a molecule can be ascribed to the increased intersystem crossing, which is favorable for enhancing the singlet oxygen generation. Therefore, the unsymmetrical PV based chromophores with heavy atom incorporation are promising singlet oxygen sensitizers for the photodynamic therapy application.

Electronic Couplings for Singlet Oxygen Photosensitization and Its Molecular Orbital Overlap Description

The reaction of triplet fusion,also named triplet-triplet annihilation,has attracted a lot of research interests because of its wide applications in photocatalytic,solar cells,and bioimaging.As for the singlet oxygen photosensitization,the reactive singlet oxygen species are generated through the energy transfers from photosensitizer(PS)to ground triplet oxygen molecule.In this work,we computed the electronic coupling for singlet oxygen photosensitization using the nonadiabatic coupling from the quantum chemical calculation.Then we utilized the molecular orbital(MO)overlaps to approximate it,where the MOs were computed from isolated single molecules.As demonstrated with quantitative results,this approach well describes the distribution of the coupling strength as the function of the intermolecular distance between the sensitizer and O_(2),providing us a simple but effective way to predict the coupling of triplet fusion reactions.

Reaction Kinetics between Thiobases and Singlet Oxygen Studied by Direct Detection of the 1O2 Luminescence Decay

Thiobase derivatives have received important investigations due to their wide usage as phototherapeutic agents and their potential carcinogenic side effects as immunosuppressants. The substitution of oxygen atom by the sulfur atom makes the ultraviolet absorption of thiobases redshifted and absorbs UVA light (>300 nm), resulting in unusual high quantum yield of triplet state to generate the singlet oxygen (1O2) through photosensitization. As a type of reactive oxygen species, 1O2 is highly reactive toward thiobases. Herein, we report the measurements of reaction rate constants between di erent thiobases and 1O2 in different solvents through the direct detection of 1O2 luminescence decay kinetics at 1270 nm. The rate constants of thiouracils with 1O2 are five times smaller than that of thioguanine with 1O2, which suggests that thiopurines are more reactive than thiopyrimidines and thus less suitable to be a photosensitive drug on the application of photodynamic therapy. Additionally, the rate constants of thiobases and 1O2 were found to be obviously influenced by the solvent polarity. With the increase of solvent polarity, the rate constants of thiobases and 1O2 decrease.

Singlet fission and its application in organic solar cells

Enhancing the power conversion efficiency(PCE)is the major task in the development of solar cells[1−5].In 1961,William Shockley and Hans J.Queisser pointed out that the highest PCE for a single-junction solar cell is limited to 31%due to the thermalization and transmission losses[6].Singlet fission(SF)is an appealing carrier-multiplication approach to break the Shockley-Queisser limit,since it converts one high-energy singlet exciton into two low-energy triplet excitons.Thus,one absorbed photon generates two electron-hole pairs.

Kinetics Study on Reaction of Atenolol with Singlet Oxygen by Directly Monitoring the^(1)O_(2)Phosphorescence

The pharmaceuti-cally active com-pound atenolol,a kind of β-blockers,may result in ad-verse effects both for human health and ecosystems if it is excreted to the surface water resources.To e ectively remove atenolol in the environ-ment,both direct and indirect photodegradation,driven by sunlight play an important role.Among indirect photodegradation,singlet oxygen(^(1)O_(2)),as a pivotal reactive species,is likely to determine the fates of atenolol.Nevertheless,the kinetic information on the re-action of atenolol with singlet oxygen has not been well investigated and the reaction rate constant is still ambiguous.Herein,the reaction rate constant of atenolol with singlet oxy-gen is investigated directly through observing the decay of the^(1)O_(2)phosphorescence at 1270 nm.It is determined that the reaction rate constant between atenolol and^(1)O_(2)is 7.0×10^(5)(mol/L)^(-1)·s^(-1)in D2O,8.0×10^(6)(mol/L)^(-1)·s^(-1)in acetonitrile,and 8.4×10^(5)(mol/L)^(-1)·s^(-1)in EtOH,respectively.Furthermore,the solvent effects on the title reaction were also inves-tigated.It is revealed that the solvents with strong polarity and weak hydrogen donating ability are suitable to achieve high rate constant values.These kinetics information on the reaction of atenolol with singlet oxygen may provide fundamental knowledge to the indirect photodegradation of β-blockers.

Parallel fluorescence and phosphorescence monitoring of singlet oxygen photosensitization in rats

The time-and spectral-resolved set-up for measurements of weak infrared luminescence of photosensitizers(PSs)and singlet oxygen using optical lightguides was used on skin of laboratory animals in vivo.Wistar rats with abdominal incisions treated by methylis aminolevulinitis(MAL)were used as a model.A control group of animals with abdominal incisions was also tested.Spectrally resolved fluorescence of the PS was acquired during the treatment from the same spot.The intensity and spectral profile of the fiuorescence signal from the skin can be used to guide the detection setup to the investigated spots in the lesion.The rate of bleaching of Protoporphyrin IX band and appearance of a band of its photoproducts during the treatment can be characterized by the exposition ED,under which the latter becomes dominant feature infiuorescence spectrum.ED value differs statistically significantly between the normal skin and the lesion treated by MAL.No direct proportionality was found between the fluorescence signal and singlet oxygen production.Nevertheless,the strong fluorescence signal is necessary but not a su±cient condition for higher singlet oxygen production in vivo.ED value correlates rather well with production of singlet oxygen,but differently in lesion and normal skin.Lifetimes of singlet oxygen differ between spots outside and in the lesion.PS triplet state lifetimes exhibit weak di®erence between spots treated and untreated by MAL.

Kinetics Study on Reaction between Dihydroartemisinic Acid and Singlet Oxygen: An Essential Step to Photochemical Synthesis of Artemisinin

Artemisinin is an excellent antimalarial drug widely used in clinical medicine.However,due to the limitation of natural source of artemisinin,the chemical synthesis of artemisinin has achieved substantial attention.Dihydroartemisinic acid is a key precursor for the synthesis of artemisinin.The reaction of dihydroartemisinic acid with singlet oxygen to form peroxide is a pivotal step in the photochemical preparation of artemisinin.Nevertheless,the reaction kinetics of dihydroartemisinic acid with singlet oxygen has not been investigated previously.Herein,we report the rate constants of the reaction between dihydroartemisinic acid and singlet oxygen.By directly detecting the luminescence decay kinetics of singlet oxygen at 1270 nm at room temperature,the reaction rate constants of singlet oxygen and dihydroartemisinic acid in different solvents are obtained to be 1.81×10^5(mol/L)^-1·s^-1 in CCl4,5.69×10^5(mol/L)^-1·s^-1 in CH3CN,and 3.27×10^6(mol/L)^-1·s^-1 in DMSO,respec-tively.It is found that the reaction rate constants of dihydroartemisinic acid with singlet oxygen increase as polarity of the solvent increases among the three solvents.These results provide fundamental knowledge to optimize experiment conditions of photochemical synthesis of artemisinin for improving the yields of artemisinin.

Monitoring of time-resolved singlet oxygen luminescence at 1270 nm by an optical fiber detection system

Singlet oxygen(^(1)O_(2))is the main cytotoxic substance in Type II photodynamic therapy(PDT).The luminescence of ^(1)O_(2) at 1270nm is extremely weak with a low quantum yield,making the direct detection of'O2 at 1270 nm very challenging.In this study,a set of highly sensitive optical fiber detection system is built up to detect the luminescence of photosensitized ^(1)O_(2) We use this system to test the luminescence characteristics of ^(1)O_(2) in pig skin tissue ex vrivo and mouse auricle skin in vivo.The experimental results show that the designed system can quantitatively detect photosensitized ^(1)O_(2) luminescence.The ^(1)O_(2) luminescence signal at 1270 nm is successfully detected in pig skin exr vivo.Compared with RB in an aqueous solution,the lifetime of ^(1)O_(2) increases to 17.4±12pus in pig skin tissue ex vivo.Experiments on living mice suggest that an enhancement of ^(1)O_(2) intensity with the increase of the TMPyP concentration.When the dose is 25 mg/kg,the vasoconstriction can reach more than 80%。The results of this study hold the potential application for clinical PDT dose monitoring using an optical fiber detection system.